On Wed, May 11 2016, Jes Sorensen wrote: > Mike Lovell <mike.lovell@xxxxxxxxxxxxx> writes: >> we have a number of systems that have a large number of software >> arrays running. its in the couple hundred range. we have been using a >> custom built kernel based on 3.4 but are wanting to update to a >> mainline kernel and have been experimenting with 4.4. the systems are >> running recent centos 6 releases but we have been downgrading the >> mdadm version from 3.3.2 in 6.7 to a custom build 3.2.6. we installed >> the downgraded version due to a problem with array numbering. i >> emailed the list a while ago explaining the issue and submitting a >> patch to fix [1]. i never heard anything back and since we had a >> simple fix i didn't follow up on it. > > [snip] > >> what do you all think? >> >> thanks >> mike >> >> [1] http://marc.info/?l=linux-raid&m=142387809409798&w=2 > > Staying consistent in using dev_t rather than casting back and forth to > int seems a reasonable fix to apply to mdadm. It obviously won't change > the issues with the newer kernels, but I don't see any reason why we > shouldn't apply that fix to mdadm. > > Neil any thoughts on this? I agree that changing "int" to "dev_t" is a good idea. We should really fix the more general problem too. On any kernel with /sys/module/md_mod/parameters/new_array find_free_devnm avoid trying anything above 511. (1<<9)-1. If that fails to find a free number, then it should probably try a name like "md_NN" and act as though ci->name is set. Also, when a "name" given for the md array that is longer than 28 bytes we need to fall back to choose an array name ourselves even if ci->name is set. Start with md_512 and work upwards. Rather than probing we should read /sys/block looking for "md_*" and maybe choose 1 more than the largest number found. Thanks, NeilBrown
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